1. Field of the Invention
The present invention relates to a system signal measurement method and apparatus.
2. Description of the Related Art
The mobile communication systems targeted by the present invention may include the 1st Generation analog, the 2nd Generation digital, the 3rd Generation IMT-2000 high speed multimedia service, and the 4th Generation ultrahigh speed multimedia service mobile communication systems.
Among the 3rd generation mobile communication systems, CDMA HRPD (High Rate Packet Data) system and WCDMA HSPA (High Speed Packet Access) are representative mobile communication systems having the channel formats for high data rate. The CDMA HRPD system is the system using Code Division Multiple Access (CDMA).
FIG. 1 is a diagram illustrating architecture of conventional HRPD system.
The HRPD system includes a Packet Data Service Node (PDSN) 101 connected to the Internet for transmitting high speed packet data to the base station 103 and a Packet Control Function (PCF) for controlling the base station 103. The base station 103 performs radio communication with plural terminals 104 and transmits high speed packet data to the terminal having the best data rate.
The 4th Generation mobile communication system evolved from the 3rd Generation mobile communication system such as HRPD system aims at the data rate of 20 Mbps or higher for high speed multimedia service. The 4th generation mobile communication system uses the orthogonal frequencies scheme such as Orthogonal Frequency Division Multiplexing (OFDM). LTE and LTE-Advanced (LTE-A) systems are under the standardization process as representative 4th generation mobile communication systems.
FIG. 2 is a diagram illustrating architecture of a typical LTE system.
The LTE system performs radio communication with plural UEs 201 and includes eNBs 202 for providing high speed multimedia service, MME/S-GWs (Serving Gateway) 203 responsible for managing UE mobility, call processing, and data path management, and a Packet Data Network Gateway (PDN-GW or P-GW) 204 connected to Internet and delivers the high speed packet data to the UE 201 via the eNBs 202.
With the advance of communications technologies, it is a tendency that conventional standalone devices operating without connection to a communication network such as control devices, metering devices, and electric appliances are being connected through wired and/or wireless communication system. Such devices connected to the communication system are capable of metering without human intermediary so as to improve efficiency and reduce maintenance cost.
Compared to the conventional human-centric communication, the communication between the communication system and the control devices, metering devices, and electric appliances are referred to as Machine to Machine (M2M) communication. In the early 1990s when the concept of M2M communication has been introduced, the remote control and telematics are considered as the examples of M2M communication and the related market has been also very limited. However, the M2M communication technology has grown rapidly to be widespread all around world as well as in our country for with the diversification of M2M-capable devices for last a few years. Particularly, the M2M communication gives a large influence in the fields such as Point Of Sales (POS) and Fleet Management in security-related application market, remote monitoring of machine and equipment, and smart metering for measuring operation time of construction equipment and metering heat and electricity consumption.
The M2M terminal has several characteristics as compared to the convention terminal. Among them, the representative characteristics are as follows.
1. The devices such as controller and moves not at all or a sporadically.
2. Some M2M terminals may perform communication of data for predetermined time duration.
3. Some M2M terminals are tolerable to delay in data communication (delay tolerant).
4. Some M2M terminals are not necessary to have voice telephony function.
5. The M2M terminal is not necessary to receive paging from the mobile communication system and but capable of requesting for connection setup when data communication is required.
6. There may be the M2M terminals greater than the conventional communication terminals in number in the area with high density population as the M2M devices are diversified.
7. The battery-powered M2M device is required to consume the battery efficiently because it may not allowed for changing the battery frequently. That is, the M2M device has to be designed to consume the power efficiently.
In the case of the M2M device operating without paging, there is no need of monitoring the messages transmitted by the eNB frequently to receive the paging. In this case, it is possible to achieve its object only by receiving the control channel sporadically to acquire the system information transmitted by the system. It is also very important technique for securing high power utilization efficiency to reduce the frequency of receiving the control channel.
In order to introduce such an operation in the LTE system, a method for increasing the system observation period in the idle state has been introduced. The period at which the UE observes the system in idle state is referred to as Discontinuous Reception (DRX) period.
FIG. 3 is a diagram illustrating the DRX periods of the conventional terminal and the M2M terminal.
In FIG. 3, the horizontal axis 301 denotes system frame number as transmission period of LTE. The M2M terminal may be designed to have the DRX period 303 which is relatively long as compared to that of the conventional terminal.
In the LTE system, the radio channel observation period is defined in association with the DRX period. That is, the UE perform received signal strength of the radio channel as many as given in the DRX period. Accordingly, if the DRX period is elongated, this means that the conventional channel variation monitoring period is elongated too and, as a consequence, the terminal cannot reflect the change in radio environment immediately. That is, even when aggregating multiple radio channel measurement results to determine cell reselection in the bad channel environment, the cell reselection determination is also delayed due to the long radio channel measurement period. This may cause a problem of paging reception failure for several DRX periods.